TABLES FOR PRACTISING 



6. Ascertain the diameter of the objects upon the slide,* using the 



inch object-glass and stage micrometer divided to looths of an 

 inch, with the aid of the neutral tint-glass reflector. 44, 62, 

 64, pi. XIII, fig. 60. PI. XII, fig. 56. 



7. What is the magnifying powers of the two French and English 



object-glasses on the table ? f 63. 



a. With the shallow eye-piece. 



b. With the deep eye-piece. 



8. Measure the angles of the crystals % upon the slide. 270*, 



pi. XLII, fig. 268. 



TABLE II. 



EXAMINATION OF OBJECTS BY DIRECT OR REFLECTED LIGHT, 

 TRANSMITTED LIGHT, AND POLARISED LIGHT. 



9. Examine the objects upon the slide and carefully note the 



different appearances produced by examining them 



1. By reflected light as opaque objects, employing 



a. The bull's-eye condenser. 27, pi. XI, figs. 51, 52. 



b. The Lieberkuhn and a stop. 30, pi. XII, fig. 53. 



2. By transmitted light, employing 



a. Direct rays. 



b. Oblique rays. PI. X, fig. 42. 



3. By polarised light. 



a. Employing the polariser and analyser only. 23, 

 pi. XIII, figs. 57, 58. 



b. After placing beneath the objects a plate of selenite. 



10. Examine some of the same crystals in different media, as de- 



scribed in 136 to 143, pi. XIX. 



a. In air. 141. 



b. In water. - 142. 



c. In turpentine, oil, or Canada balsam. 143. 



* Fragments of human hair. 



t French quarter and one inch. English quarter and one inch. 



J Crystals of cholesterine. 



Spherical crystals of carbonate of lime or starch globules. 



